nt - p h / 03 07 06 5 v 1 9 J ul 2 00 3 Teleportation in a noisy environment : a quantum trajectories approach

We study the fidelity of quantum teleportation for the situation in which quantum logic gates are used to provide the long distance entangle-ment required in the protocol, and where the effect of a noisy environment is modeled by means of a generalized amplitude damping channel. Our results demonstrate the effectiveness of the quantum trajectories approach, which allows the simulation of open systems with a large number of qubits (up to 24). This shows that the method is suitable for modeling quantum information protocols in realistic environments. The practical implementation of any quantum information protocol has to face the problem of the unavoidable coupling of quantum processors with their environment. Indeed, real systems can never be perfectly isolated from the surrounding world. It is therefore important to understand the impact of the coupling with a noisy environment on the stability of quantum protocols. In particular, the simulation of these protocols including realistic models of noise, promises to give useful insights for the design and future construction of quantum hardware. As a consequence of the unwanted environmental coupling, a quantum processor becomes, in general, entangled with its environment. Therefore its state is described by a density matrix, whose evolution is ruled, under the assumption that the environment is Markovian, by a master equation. Solving this equation for a state of several qubits is a prohibitive task in terms of memory cost. Instead of doing so, quantum trajectories allow us to store only a stochastically 1